Method for producing hydrogen and apparatus for supplying hydrogen

ABSTRACT

With a method producing hydrogen by making iron or iron oxide contact water, water vapor, or a gas including water vapor, a hydrogen generating medium, which has a high hydrogen generation reaction rate and is resistant to a repetition of oxidation-reduction without degrading its activity, is provided by adding a different metal (such as Ti, Zr, V, Nb, Cr, Mo, Al, Ga, Mg, Sc, Ni, Cu, etc.) other than the iron to the iron or the iron oxide.

TECHNICAL FIELD

[0001] The present invention relates to a technique decomposing water,and efficiently producing hydrogen.

BACKGROUND ART

[0002] Partial oxidation or water vapor reforming, which uses oil ornatural gas as a raw material, generates a lot of carbon dioxide gas atthe time of hydrogen synthesis. Therefore, a UT-3 cycle using solarheat, and a method disclosed by Japanese Patent Publication No.07-267601 are proposed as a method that does not generate a carbondioxide gas. However, this method requires a large-scale system in orderto use solar heat, and also the cost of the large-scale system becomesvery high.

[0003] Additionally, many proposals using a hydrogen storing alloy aremade as means for safely storing/carrying hydrogen instead of ahigh-pressure steel bottle. However, there are problems that a highhydrogen pressure is required to make a hydrogen storing alloy occludehydrogen, and the hydrogen storing alloy cannot be used in an atmosphereof air and water vapor, which costs very high.

[0004] For a fuel cell using hydrogen and air as raw materials, a methodsupplying hydrogen with methanol or gasoline steam reforming is general,and a number of inventions are made. With these methods, however, carbonmonoxide and a carbon dioxide gas occur simultaneously. Especially, forcarbon monoxide, a device for reducing carbon monoxide to 10 ppm or lessis required due to a problem that an electrode of a fuel cell ispoisoned, which leads to a high cost.

[0005] As a method producing hydrogen from water, a steam iron method isknown. This method is a method using oxidation-reduction(Fe→FeO(Fe₃O₄)→Fe) of only iron as a reaction. For the reaction, atemperature, by way of example, equal to or higher than 600° C. isrequired. If oxidation-reduction is repeated, there is a disadvantagethat so-called sintering which agglomerates metallic iron occurs, andthe activity of the metallic iron is rapidly degraded. Accordingly, ahydrogen generating medium (oxidation-reduction material) which does notmake a sintering phenomenon occur, is superior in resistance, andexhibits high activity is demanded.

DISCLOSURE OF INVENTION

[0006] An object of the present invention is to provide a methodefficiently decomposing water and producing hydrogen by providing ahydrogen generating medium (oxidation-reduction material) that has ahigh hydrogen generation reaction rate, and is resistant to a repetitionof oxidation-reduction without degrading its activity.

[0007] The method producing hydrogen by making iron or iron oxidecontact water, water vapor, or a gas including water vapor ischaracterized in that a different metal other than the iron is added tothe iron or the iron oxide as recited in claim 1, in order to achievethe above described object.

[0008] In the present invention, water used as a raw material may notalways be purified water, but tap water, industrial water, or the likeis used.

[0009] Additionally, for the ion used in the present invention, pureiron, iron oxide, or an iron compound such as iron nitrate, etc. is usedas a raw material.

[0010] Furthermore, a metal added and used in the present invention isat least one of metals of the fourth family, the fifth family, the sixthfamily, and the thirteenth family of the IUPAC periodic table.Desirably, a selection is made from among Ti, Zr, V, Nb, Cr, Mo, Al, andGa. Or, any of Mg, Sc, Ni, and Cu is available.

[0011] The amount of addition of a different metal added to iron or ironoxide is calculated with the number of moles of atoms of the metal.Desirably, the amount of addition is prepared to be 0.5 to 30 mol % ofatoms of all metals. More desirably, the amount of addition is preparedto be 0.5 to 15 mol %.

[0012] A metal adding method is implemented by a physical mixture or animpregnation method, or desirably, a coprecipitation method. For aprepared iron compound, a shape having a large surface area such aspowder state, pellet type, cylindrical shape, honeycomb structure,nonwoven fabric form, etc., which is suitable for reaction, is selectedto be efficiently used, and utilized for a decomposition reaction ofwater.

[0013] This iron compound is included in a reactor, and reduced withhydrogen, etc. Hydrogen is produced by making the reduced iron compoundcontact water, water vapor, or a gas including water vapor. At thistime, the iron which reacts with water becomes iron oxide. Note thatthis oxidation/reduction reaction can be also made at a low temperatureof 600° C. or lower.

[0014] According to the present invention, hydrogen can be supplied atlow cost without generating carbon monoxide, which poisons the electrodeof a fuel cell, to a fuel cell for a local facility, a plant, home, or avehicle. The produced hydrogen is used not only for a fuel cell but alsoas an extensible hydrogen supplying means such as a hydrogen burner,etc. Additionally, the reduced iron compound is filled in a container,which is made available as a hydrogen supplying means to the abovedescribed fuel cell, etc. in the form of a portable hydrogen supplyingcassette.

[0015] Furthermore, according to the present invention, a hydrogensupplying apparatus is configured by a portable cassette, which includesa hydrogen generating medium inside and comprises at least two pipeinstalling means, wherein a main component of the hydrogen generatingmedium is iron or iron oxide, to which a different metal is added, andthe cassette, into which water or water vapor is poured via one of thepipe installing means, can supply hydrogen produced by decomposing thewater to a hydrogen consuming device from the other communicating porepipe installing means is provided.

[0016] A heater may be arranged within the cassette. Furthermore, a pipethat supplies inert gas or air may be arranged in the cassette.

[0017] Iron oxidized by reacting with water is again reduced byhydrogen, etc., and repeatedly available as an oxidation-reductionmedium without degrading its activity.

[0018] As the reason that the above described effects can be obtained,prevention of sintering, promotion of an oxygen diffusion rate within asolid, an improvement in a water decomposition activity on a surface,etc. are considered.

BRIEF DESCRIPTION OF DRAWINGS

[0019]FIGS. 1A and 1B are schematic views of a reaction system of aniron compound used in a preferred embodiment of the present invention,and respectively show a reduction reaction process and a waterdecomposition reaction process;

[0020]FIGS. 2A to 2E are schematics showing the states of a waterdecomposition reaction and a reduction reaction in the case of ironoxide with Ga added, iron oxide with Mo added, iron oxide with Al added,iron oxide with Zr added, and only iron oxide, FIGS. 2A, 2C, and 2Erespectively show a first, a second, and a third water decompositionreaction, and FIGS. 2B and 2D respectively show a first and a secondreduction reaction;

[0021]FIGS. 3A to 3E show the states of a water decomposition reactionand a reduction reaction in the case of iron oxide with Sc added, ironoxide with Cr added, iron oxide with V added, and only iron oxide, FIGS.3A, 3C, and 3E respectively show a first, a second, and a third waterdecomposition reaction, and FIGS. 3B and 3D respectively show a firstand a second reduction reaction;

[0022]FIG. 4 is a graph representing hydrogen generation reaction ratesat the time of water decomposition reaction;

[0023]FIGS. 5A to 5E show the effects produced by a metal adding methodaccording to the present invention, FIGS. 5A, 5C, and 5E respectivelyshow a first, a second, and a third water decomposition reaction, andFIGS. 5B and 5D respectively show a first and a second reductionreaction;

[0024]FIG. 6 shows a hydrogen supplying apparatus having a configurationwhere a reaction container in which an oxidation/reduction iron medium(iron oxide with a metal of the present invention added) is included,and a water supplying apparatus are connected with a pipe; and

[0025]FIG. 7 shows the state where a cassette in which anoxidation/reduction iron medium is included is connected to a fuel cell.

BEST MODE OF CARRYING OUT THE INVENTION

[0026] Schematic views of a reaction system of an iron compound used inone preferred embodiment of the present invention are shown in FIGS. 1Aand 1B. FIG. 1A shows a reduction reaction process, whereas FIG. 1Bshows a water decomposition reaction process implemented by the ironcompound reduced in FIG. 1A, and water vapor. The apparatus shown inFIGS. 1A and 1B configures a closed gas circulatory system reactionapparatus by connecting a reactor 1 and a gas circulatory pump 2 withglass pipes 3 and 4. Additionally, a pressure indicator 5 measuring thepressure of a gas within the system is connected to the glass pipe 4. Bymeasuring the pressure of the gas within the system with the pressureindicator 5, the amount of reduction (an amount calculated from theamount of consumption of hydrogen used for the reduction), etc. can bemeasured.

[0027] In the reduction reaction process shown in FIG. 1A, the reactor 1is heated to, for example, on the order of 330° C. by an electricfurnace 6, and the following reduction reaction occurs.

[0028] FeO_(x)+H₂→FeO_(x−1)+H₂O

[0029] A water vapor trap 7 is arranged in the downstream of the reactor1. This water vapor trap 7 is cooled down by dry-ice ethanol, and thetemperature of the dry ice is set to, for example, on the order of −76°C. Water generated by the above described reduction reaction iscoagulated within the water vapor trap 7, and removed from the system.

[0030] In the water decomposition reaction process shown in FIG. 1B, thereactor 1 is heated to, for example, on the order of 380° C. by theelectric furnace 6, and the following water decomposition reactionoccurs.

[0031] FeO_(x−1)+H₂O→Fe0_(x)+H₂

[0032] The water coagulated by the water vapor trap device 7 (watergenerated by reducing the iron compound) shown in FIG. 1A is evaporatedby being warmed with cold water, for example, to 14° C. this time.

[0033] The iron compound included in the reactor 1 is prepared with thefollowing coprecipitation method (urea method). Namely, 0.0194 mol ofiron nitrate (III) 9-hydrate (Fe(NO₃)₃.9H₂O: manufactured by Wako PureChemical Industries, Ltd.), 0.0006 mol of nitrate salt of added gallium(Ga(NO₃)₃.9H₂O: manufactured by Wako Pure Chemical Industries, Ltd.),and 1.0 mol of urea as a precipitant are added and dissolved in 1 literof water deaerated by ultrasonic wave for 5 minutes. The mixed solutionis heated to 90° C. while being stirred, and kept to be the sametemperature for 3 hours. After the reaction terminates, the solution isleft untouched and precipitated for 48 hours, and suction-filtrated. Theprecipitate is dried at 80° C. for approximately 24 hours. Thereafter,the precipitate is air-burned at 300° C. for 3 hours, and at 500° C. for10 hours. The amount of iron within the sample is checkweighed to be 50mg as ferric oxide (Fe₂O₃), and atoms of the added metal are prepared tobe 3 mol % of atoms of all metals.

[0034] Before the reduction reaction with hydrogen is made, the sampleis included in the reactor 1, and vacuum-pumped for 30 minutes afterbeing heated to 400° C. Oxygen having a partial pressure ofapproximately 8.0 kPa is made to contact the sample for 1 hour so as tobe completely oxidized. Thereafter, vacuum pumping for 30 minutes ormore is again performed until the degree of vacuum reaches 1.3×10⁻⁵ kPaor lower. In a preferred embodiment to be described below, vacuumpumping for 30 minutes or more is performed until the degree of vacuumreaches 1.3×10⁻⁵ kPa or lower, before the reduction reaction and thewater decomposition reaction for producing hydrogen by making watervapor contact.

[0035] Next, the reduction reaction shown in FIG. 1A is made as follows.Namely, hydrogen is introduced to the apparatus so that the initialpressure becomes 33.3 kPa, and the hydrogen is made to contact thesample at 330° C. The degree of reduction is estimated with the amountof consumption of the hydrogen within the system, and the reaction isterminated when ferric oxide (Fe₂O₃) within the sample reaches thedegree of reduction 80% (the amount of hydrogen within the system isapproximately 190 μmol). The degree of reduction referred to here is anumeric value converted on the assumption that the state of the ferricoxide (Fe₂O₃) is the degree of reduction 0%, and the state of metalliciron (Fe) is the degree of reduction 100% as shown in a lower portion ofFIG. 1A.

[0036] After the reduction reaction with hydrogen is terminated, thewater decomposition reaction shown in FIG. 1B is made as follows.Namely, water is introduced to the apparatus, and the introduced waterand the water generated by the reduction reaction are combined to be9.39×10⁻⁴ mol, and kept to be 14° C. At this time, the pressure of watervapor is approximately 1.5 kPa. Argon is introduced so that its initialpressure becomes 12.5 kPa. After the argon is circulated for 10 minutes,it is made to contact the sample at 380° C. The degree of reduction isestimated with the amount of generation of hydrogen within the system,and the reaction is terminated when the degree of reduction of ironoxide within the sample is restored to 30% (the amount of hydrogenwithin the system is approximately 660 μmol)

[0037] After the above described water decomposition reaction isterminated, the reduction reaction is again made, and the waterdecomposition reaction is made 3 times in total. States of the waterdecomposition reaction and the reduction reaction in practical examplesof iron oxide with Ga added (marked with ◯), iron oxide with Mo added(marked with Δ), iron oxide with Al added (marked with □), and ironoxide with Zr added (marked with x) are shown in FIGS. 2A to 2E. A mark in FIGS. 2A to 2E shows a comparison example of a result of using onlyiron oxide prepared with a coprecipitation method (urea method) for thewater decomposition/reduction reaction. Also this example is preparedunder a condition similar to the above described one.

[0038] That is, in FIG. 2A, for example, a sample prepared by reducingiron oxide with gallium added, which is prepared with the abovedescribed coprecipitation method (urea method), to 80% is made tocontact water vapor generated by evaporating water agglutinated from thewater vapor trap device at a time 0 minute, so that hydrogen isgenerated (indicated by a mark ◯ in FIG. 2A).

[0039] The reduced iron oxide with gallium added is again oxidized byoxygen which occurs due to water decomposition. The reaction isterminated when the degree of reduction of the iron oxide with galliumadded reaches 30% (oxidized from 80 to 30%) (the amount of hydrogenwithin the system is approximately 660 μmol), and generated hydrogen isvacuum-pumped.

[0040] In FIG. 2B, hydrogen of approximately 660 μmol is newlyintroduced to the system, and the reduction reaction of the iron oxidewith gallium added, which is oxidized in FIG. 2A, is made. The reactionis terminated when the degree of reduction of the iron oxide withgallium added reaches 80% while the hydrogen within the system is beingconsumed (the amount of hydrogen within the system is approximately 190μmol).

[0041]FIG. 2C shows the second water decomposition reaction, FIG. 2Dshows its subsequent reduction reaction, and FIG. 2E shows the thirdwater decomposition reaction.

[0042] In FIG. 2C, with the water decomposition reaction only with ironoxide, it takes approximately 90 minutes that the amount of hydrogenwithin the system increases from approximately 190 μmol to approximately660 μmol. In the meantime, with the water decomposition reaction withthe iron oxide with gallium added according to the present invention,the amount of hydrogen can reach approximately 660 μmol forapproximately 5 minutes.

[0043] In FIG. 2D, the reduction reaction of the iron oxide with galliumadded according to the present invention can shorten its reaction timein comparison with the reduction reaction only with iron oxide.

[0044] In FIG. 2E showing the third water decomposition reaction, thewater decomposition reaction only with iron oxide is not restored toapproximately 660 μmol (the degree of reduction is 30%) although 210minutes are elapsed. In the meantime, the water decomposition reactionusing the iron oxide with gallium added according to the presentinvention can reach approximately 660 μmol (the degree of reduction is30%) for approximately 5 minutes almost unchanged as the first waterdecomposition reaction.

[0045] States of the water decomposition reaction and the reductionreaction in the case of only iron oxide prepared with a coprecipitationmethod (urea method), and in the case of a sample to which metals (ironoxide with Sc added, iron oxide with Cr added, and iron oxide with Vadded) other than the metals added in FIGS. 2A to 2E are added are shownin FIGS. 3A to 3E.

[0046] It can be proved also from these results that the efficiency ofthe water decomposition/reduction reaction is significantly improvedalso by adding the metals such as Sc, Cr, V, etc.

[0047] Table 1 represents results obtained by comparing

[0048] Table 1 represents results obtained by comparing a hydrogengeneration reaction rate (namely, a numerical value representing theslope of a curve from the amount of hydrogen approximately 280 toapproximately 370 μmol (the degree of reduction 70 to 60%) within thesystem) at the time of the water decomposition reaction represented bythe graphs shown in FIGS. 2A to 2E and 3A to 3E, and FIG. 4 is agraphical representation of Table 1. In Table 1 and FIG. 4, results ofexperiments similar to those shown in FIGS. 2A to 2E and 3A to 3E aredepicted as practical examples 1 to 18 and a comparison example 1 alongwith the results obtained with the sample to which metals (Ni, Cu, Ti,Mg, Nb, Co, Ca, Mn, Zn, Y, and Ce) other than the above described metalsare added. TABLE 1 ADDITIVES WATER DECOMPOSITION MAIN MATERIAL NAME OFREACTION RATE (μmol/min) (IRON NITRATE) ELEMENT USED REAGENT FIRSTSECOND THIRD COMPARISON EXAMPLE 1 Fe (NO₃)₃.9H₂O — NO ADDITIVES 48.917.7 12.8 PRACTICAL EXAMPLE 1 Fe (NO₃)₃.9H₂O Ga Ga(NO₃)₃.nH₂O 126.2128.0 113.4 PRACTICAL EXAMPLE 2 Fe (NO₃)₃.9H₂O Cr Cr(NO₃)₃.9H₂O 90.4119.5 94.2 PRACTICAL EXAMPLE 3 Fe (NO₃)₃.9H₂O V NH₄VO₃ 114.2 126.5 75.8PRACTICAL EXAMPLE 4 Fe (NO₃)₃.9H₂O Mo (NH₄)₆Mo₇O₂₄.4H₂O 106.8 91.5 89.3PRACTICAL EXAMPLE 5 Fe (NO₃)₃.9H₂O Al Al(NO₃)₃.9H₂O 82.3 93.3 88.4PRACTICAL EXAMPLE 6 Fe (NO₃)₃.9H₂O Sc Sc(NO₃)₃.4H₂O 72.0 80.9 88.6PRACTICAL EXAMPLE 7 Fe (NO₃)₃.9H₂O Zr ZrCl₂O.8H₂O 35.5 57.5 65.7PRACTICAL EXAMPLE 8 Fe (NO₃)₃.9H₂O Ti (NH₄)₂TiO(C₂O₄)₂.2H₂O 30.2 48.959.7 PRACTICAL EXAMPLE 9 Fe (NO₃)₃.9H₂O Mg Mg(NO₃)₂.6H₂O 57.7 36.0 20.9PRACTICAL EXAMPLE 10 Fe (NO₃)₃.9H₂O Nb NIOBIUM OXALATE(18.6 wt % Nb₂O₅)21.2 22.2 23.7 COMPARISON EXAMPLE 2 Fe (NO₃)₃.9H₂O Ca Ca(NO₃)₂.4H₂O 23.413.4 10.5 COMPARISON EXAMPLE 3 Fe (NO₃)₃.9H₂O Mn Mn(NO₃)₂.6H₂O 27.3 14.08.6 COMPARISON EXAMPLE 4 Fe (NO₃)₃.9H₂O Co Co(NO₃)₂.6H₂O 40.4 13.2 6.3COMPARISON EXAMPLE 5 Fe (NO₃)₃.9H₂O Ni Ni(NO₃)₂.6H₂O 93.1 37.2 12.4COMPARISON EXAMPLE 6 Fe (NO₃)₃.9H₂O Cu Cu(NO₃)₂.3H₂O 66.1 26.0 12.0COMPARISON EXAMPLE 7 Fe (NO₃)₃.9H₂O Zn Zu(NO₃)₂.6H₂O 44.0 25.1 12.0COMPARISON EXAMPLE 8 Fe (NO₃)₃.9H₂O Y Y(NO₃)₃.6H₂O 9.1 8.2 8.9COMPARISON EXAMPLE 9 Fe (NO₃)₃.9H₂O Ce Ce(NO₃)₃.6H₂O 9.0 11.6 15.0

[0049] It is proved from Table 1 and FIG. 4 that the hydrogen generationreaction rate is significantly improved, and also a degradation of theactivity due to a repetition of the water decomposition reaction can beprevented according to the present invention which adds a metal otherthan iron to iron or iron oxide. Note that niobium (Nb) in a practicalexample 12 is a very stable substance the activity of which is notdegraded by a repetition, although its first hydrogen generationreaction rate is not so high.

[0050] Furthermore, in the water decomposition reaction experiments inthese practical examples, for added metals (Co, Ca, Mn, Zn, Y, and Ce),which are not included in claims 2 to 4, their hydrogen generationreaction rates do not become significantly high, but some of theiractivities are degraded slightly by a repetition of the waterdecomposition/reduction reaction experiment. In Table 1 and FIG. 4, thewater decomposition/reduction reaction experiment is repeated only threetimes. However, an effect of improving the efficiency of hydrogengeneration can possibly become high if the experiment is repeated manytimes. Therefore, a study is being made by conducting additionalexperiments at present.

[0051] Next, effects produced by the metal adding method according tothe present invention are shown in FIGS. 5A to 5E. Namely, comparisonsof the water decomposition/reduction reaction among a sample prepared byadding zirconium with a coprecipitation method (urea method), a sampleprepared by adding zirconium with an impregnation method, andcommercially available ferric oxide powder (Fe₂O₃: manufactured by WakoPure Chemical Industries, Ltd.) are shown in FIGS. 5A to 5B.

[0052] As the coprecipitation method (urea method), a method similar tothe above described one is executed, and its results are as describedabove.

[0053] A method adding zirconium with the impregnation method isexecuted as follows. 4.52×10⁻⁴ mol of chloride salt of added zirconium(ZrCl₂O.8H₂O: manufactured by Kanto Kagaku) is dissolved in 60 ml ofwater, and 0.0146 mol of ferric oxide (Fe₂O₃: manufactured by Wako PureChemical industries, Ltd.) is added while being stirred at 80° C. Afterthe solution is dried at 120° C., its precipitate is air-burned at 300°C. for 2 hours and at 500° C. for 5 hours.

[0054] With both of the coprecipitation method (urea method) and theimpregnation method, atoms of the added zirconium are prepared to be 3mol % of atoms of all metals, and the amount of iron is checkweighed tobe 50 mg as ferric oxide (Fe₂O₃)

[0055] Furthermore, also the commercially available ferric oxide powder(Fe₂O₃: manufactured by Wako Pure Chemical Industries, Ltd.) ischeckweighed to be 50 mg.

[0056] Note that a preprocess of the sample is performed as describedabove.

[0057]FIG. 5A shows the first water decomposition reaction made byintroducing water vapor at a reaction time 0 minute, and by making asample contact the water vapor to generate hydrogen.

[0058]FIG. 5B shows its subsequent reduction reaction, FIG. 5C shows thesecond water decomposition reaction, FIG. 5D shows its subsequentreduction reaction, and FIG. 5E shows the third water decompositionreaction.

[0059] In FIGS. 5A to 5E, □ indicates the water decomposition/reductionreaction of a sample prepared with a coprecipitation (urea) method, Δindicates the water decomposition/reduction reaction of a sampleprepared with an impregnation method, and ◯ indicates the waterdecomposition/reduction reaction of commercially available ferric oxidepowder.

[0060] As the number of times of the water decomposition reaction of thecommercially available ferric oxide powder increases, the hydrogengeneration reaction rate becomes lower, and a long time is requireduntil the reaction reaches approximately 660 μmol (the degree ofreduction is 30%). In the meantime, the water decomposition reaction ofthe sample prepared with the impregnation method reaches approximately660 μmol in a shorter time than the water decomposition reaction of thecommercially available ferric oxide powder. Furthermore, the time periodduring which the water decomposition reaction of the sample preparedwith the coprecipitation method (urea method) becomes significantlyshort until the reaction reaches approximately 660 μmol. In FIG. 5E, thereaction reaches approximately 660 μmol in 10 minutes.

[0061] Furthermore, also the reduction reaction of the sample preparedwith the coprecipitation method (urea method) requires shorter time thanthat of the reduction reaction of the commercially available ferricoxide powder until the reaction reaches approximately 190 μmol (thedegree of reduction 80%) as shown in FIG. 5D.

[0062] As presented above, the water decomposition/reduction reactionefficiency of the sample prepared with the impregnation method becomeshigher than that of the commercially available ferric oxide powder, andthe water decomposition/reduction reaction of the sample prepared withthe coprecipitation method (urea method) significantly increases inefficiency, and its activity is not degraded even if waterdecomposition/reduction is repeated.

[0063] Table 2 represents results of the hydrogen generation reactionrate when a water decomposition reaction is respectively made once atdifferent temperatures (250° C. and 400° C.) by using a sample of onlyiron oxide and iron oxide with gallium added, which is prepared with acoprecipitation method (urea method) similar to the above described one(a method calculating the hydrogen generation reaction rate is similarto the above described one). TABLE 2 WATER DECOMPOSITION ADDITIVESREACTION RATE MAIN MATERIAL NAME OF (μmol/min) (IRON NITRATE) ELEMENTUSED REAGENT 250° C. 400° C. COMPARISON Fe(NO₃)₃.9H₂O — NO ADDITIVES 0.511.2 EXAMPLE 2 PRACTICAL Fe(NO₃)₃.9H₂O Ga Ga(NO₃)₃.nH₂O 13.3 169.1EXAMPLE 19

[0064] As represented by Table 2, the reaction rate of the iron oxidewith gallium added (practical example 19) becomes faster approximately15 times the sample using only iron oxide (comparison example 2) at areaction temperature of 400° C. Additionally, the reaction rate of theiron oxide with gallium added at 250° C. is close to that of the sampleusing only the iron oxide at 400° C. The reaction temperature is droppedby using the iron oxide with gallium added, which is very effective atreducing hydrogen supply energy to a system (such as a fuel cell, etc.)which requires hydrogen.

[0065] A preferred embodiment of a hydrogen supplying apparatus thatadopts the method according to the present invention is shown in FIG. 6.The apparatus shown in FIG. 6 has a configuration where a reactioncontainer 11 in which an oxidation/reduction iron medium (iron oxide towhich a metal according to the present invention is added) 19 isincluded, and a device 12 for supplying water is connected with a pipe13, and the whole of the configuration is structured as a cassette 20for supplying hydrogen. In the above described practical examples, theexperiments are conducted with the closed gas circulatory reactiondevice, whose reaction system is closed. However, the present inventioncan be used for the reaction of a gas distribution type as shown in FIG.6.

[0066] The reaction container 11 which makes a waterdecomposition/reduction reaction is connected to the water supplyingdevice 12 with the pipe 13, and the water supplying device 12 isconnected to a pipe which introduces inert gas or air. As the inert gas,for example, nitrogen, argon, helium, etc. are used. Nitrogen (inertgas) is used as a carrier gas for smoothly making a reaction or to vergeair (oxygen) within the system, but it is not always required. Also airis used as a carrier gas for smoothly making a reaction, and not alwaysrequired. Water within the cassette 20 is sometimes connected to a pipe15 so as to be filled in the water supplying device 12 from the outsideof the cassette 20 depending on need.

[0067] The reaction container 11 is connected to a pipe 16 for emittinghydrogen or water vapor, makes a water decomposition reaction, andtransmits generated hydrogen to a system such as a polymer electrolytefuel cell, etc., which requires hydrogen. As a heat source whichsupplies heat for a water decomposition/reduction reaction or waterevaporation, a heater 17 is arranged within the cassette 20. The heatsource may be any of a generally used electric furnace, a heater,induction heat, catalytic combustion heat, and heat generated bychemical reaction. The reaction container 11 is made of a metal such asstainless steel, aluminum, etc., ceramic such as alumina, zirconia,etc., heat-resistant plastic such as phenol, polyphenylene sulfide,etc., and has a structure resistant to heat or internal and externalpressure.

[0068] In the cassette 20, a heat insulating material 17 a such assilica fiber, etc. is inserted, and hidden by a cover 21. A filter 18 isrespectively arranged at a gas introduction/emission vent of thecassette 20.

[0069] Additionally, the water supplying device 12 is arranged withinthe cassette 20 in the preferred embodiment shown in FIG. 6. However,water may be directly supplied to the reaction container 11 from thepipe 15 for supplying water without arranging the water supplying device12, and inert gas including water vapor or air may be introduced fromthe pipe 14. Furthermore, the heater 17 is arranged within the cassette20 in this preferred embodiment. However, the heater may not be arrangedwithin the cassette 20 and may be arranged separately from the cassette.

[0070]FIG. 7 shows the state where the cassette 20 in which a reducedoxidation/reduction iron medium is included is connected to a polymerelectrolyte fuel cell 30. The reduced oxidation/reduction iron medium 19and water react with each other, so that hydrogen is generated from thecassette 20. The generated hydrogen is supplied to a fuel electrode 31of the polymer electrolyte fuel cell 30 via a pipe 25 connected to thepolymer electrolyte fuel cell 30. To an air electrode 32 of the polymerelectrolyte fuel cell 30, air is introduced, and electric energy isextracted by the reaction of hydrogen and oxygen within the air.

[0071] Since the hydrogen producing method according to the presentinvention is configured as described above, the following effects can beobtained.

[0072] A hydrogen generation reaction rate, and the total amount ofhydrogen generation per unit weight are improved by adding a differentmetal other than iron to iron or iron oxide, whereby hydrogen can besupplied very efficiently to a system such as a polymer electrolyte fuelcell, which requires hydrogen.

[0073] Additionally, an oxidation/reduction iron medium which hasgenerated hydrogen can be recycled by being again reduced, and itsactivity is not degraded even if it is repeatedly used.

[0074] Furthermore, a reaction rate becomes faster 15 times at areaction temperature of 400° C. in the case where iron oxide withgallium added is used, in comparison with the reaction in the case whereonly iron oxide is used. If iron oxide with gallium added is used, 250°C. is sufficient as a reaction temperature, which is very effective atreducing hydrogen supply energy to a system (such as apolymerelectrolyte fuel cell, etc.), which requires hydrogen.

[0075] Even if a metal other than iron, which is added according to thepresent invention, is expensive, an amount as small as 3 mol % iseffective at increasing a reaction efficiency. Therefore, hydrogen canbe produced at low cost.

[0076] Still further, gas generated from the cassette does not containimpurities other than pure hydrogen and water vapor in the presentinvention. Therefore, a fuel electrode of a low-temperature operatingfuel cell (a proton-exchange membrane type, a phosphoric type, a KOHtype, etc.) is not poisoned. In addition, the present invention isconfigured by a simple system without a CO removal device. This producesa high economic effect.

INDUSTRIAL APPLICABILITY

[0077] The present invention is available as a hydrogen supplying meansthat can supply hydrogen at low cost without generating carbon monoxide,which poisons an electrode of a fuel cell, to a fuel cell for a localfacility, a plant, home, or a vehicle as described above. Producedhydrogen is used not only for a fuel cell, but also for an extensivefield such as a hydrogen burner, etc. Additionally, a reduced ironcompound is filled in a container, which is available as a hydrogensupplying means to a fuel cell, etc., in the form of a portable hydrogensupplying cassette.

1. A hydrogen producing method producing hydrogen by making iron or ironoxide contact water, water vapor, or a gas including water vapor,comprising adding a different metal other than the iron to the iron orthe iron oxide.
 2. The hydrogen producing method according to claim 1,wherein the added metal is at least one of a fourth family, a fifthfamily, a sixth family, and a thirteenth family of a periodic table. 3.The hydrogen producing method according to claim 1, wherein the addedmetal is at least one of Ti, Zr, V, Nb, Cr, Mo, Al, and Ga.
 4. Thehydrogen producing method according to claim 1, wherein the added metalis at least one of Mg, Sc, Ni, and Cu.
 5. The hydrogen producing methodaccording to claim 3 or 4, wherein the metal is added with acoprecipitation method.
 6. A hydrogen supplying apparatus, configured bya portable cassette (20), which includes a hydrogen generating medium(19) and comprises at least two pipe installing means (13 and 16),wherein: a main component of the hydrogen generating medium (19) is ironor iron oxide, to which a different metal is added; and the cassette(20), into which water or water vapor is poured via one (13) of the pipeinstalling means, can supply hydrogen, which is generated by decomposingthe water, from the other communicating pore pipe installing means (16)to a hydrogen consuming device (30).
 7. The hydrogen supplying apparatusaccording to claim 6, wherein a heater (17) is arranged within thecassette (20).
 8. The hydrogen supplying apparatus according to claim 6or 7, wherein a pipe (14) which supplies inert gas or air is arranged inthe cassette (20).